# L-22 MCS 260 Wed 3 Mar 2008 : questions
#
# The module questions generates questions,
# shuffles the answers, evaluates the choice,
# and keeps the tally of right and wrongs.

import quand

def generate():
   """
   Returns a multiple choice question
   as a tuple (q,L), where q is a number,
   and L is a list of numbers with answers.
   """
   import random
   q = random.randint(1,len(quand.questions))
   L = range(1,len(quand.answers[q])+1)
   return (q,L)

def shuffle(L):
   """
   Shuffles the order of the answers
   on return is a permutation of the list L.
   """
   import random
   n = len(L)
   b = L
   s = []
   while n > 0:
      i = random.randint(0,n-1)
      s.append(b.pop(i))
      n = n - 1
   return s

def evaluate(L,c):
   """
   Evaluates choice c to True or False
   where L is a list of answers.
   """
   return (L[c-1] == 1)

def update_tally(t,b):
   """
   Updates tally of True or False answers
   where t is a list of two elements and
   b is True or False, returns the updated tally.
   """
   nt = t
   if b:
      nt[1] += 1
   else:
      nt[0] += 1
   return nt